Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description earns credit for disclosing the domain rule the tool encodes (the ~50 weekly conversions learning-phase threshold), which is real behavioral context absent from structured fields. It stops short of describing what the response contains (verdict, gap to threshold), so not a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The core purpose is front-loaded in a single sentence with no wasted clauses. The trailing promotional URL is not an operational requirement and slightly dilutes otherwise tight copy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description should say what comes back (feasible/not-feasible, conversion shortfall, required budget), and it does not — nor does it explain that the check is roughly (dailyBudget/estCpa)*7 versus 50. It gives the threshold but not the verdict shape, leaving a real gap for a computation-only tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for both parameters (dailyBudget, estCpa), so the schema carries the semantics. The description adds no format, unit, currency, or horizon detail beyond what the schema already states; baseline 3 is correct.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('check') and a sharply bounded resource: whether a small daily budget yields the ~50 weekly conversions needed to exit the platform learning phase. That framing is distinctive against siblings like ad_spend_waste_calculator or linkedin_ad_cost_threshold_calculator, which an agent can tell apart without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The phrase 'small daily ad budget' and 'exit the learning phase' imply a context, but there is no explicit when-to-use, no when-not-to-use, and no named alternative among the many budget/CAC siblings. The agent is left to infer applicability entirely.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.